Without limiting the scope of the invention, its background is described in connection with electrochemical removal of bromide from water.
Bromide removal is necessary before wastewater can be discharged into natural water bodies to avoid post-discharge trihalomethanes formation. Bromate formation must be minimized during bromide conversion due to its well-established detrimental health effects and difficulty of removal from water once generated.
Typical sources of bromide contamination are coal-fired power plant wastewater and oil field wastewater. The present invention includes applications in power and oil/gas industries. In coal-fired power plants, bromine is present in the organic matter precursor of coal and is often added during combustion to oxidize elemental mercury. During the burning of coal and oxidation of mercury, bromine is converted to bromide and is found in coal-fired power plant wastewater, and may be discharged to natural water.
Surface and groundwater are a major source of drinking water, and natural organic matter is present in significant quantities in most sources. Disinfection is typically a necessary step to generate quality drinking water for the public, and chlorination is an extensively used method. If bromide is present during chlorination, it can be oxidized by chlorine into hypobromous acid (HOBr) which can react to form various brominated forms of trihalomethanes (THMs) which may cause cancer in the gastro-intestinal tract, spontaneous abortion, birth defects, and still births. Removal of brominated THMs is well known to be technically difficult.
U.S. Patent Application Publication No. 2012/0160706, entitled, “Apparatus and Method for Electrochemical Treatment of Wastewater,” discloses an electro-coagulation unit for removing contaminants with at least one anode and at least one cathode and an electro-oxidation unit for oxidizing contaminants wherein oxidants are electrochemically generated.
U.S. Pat. No. 7,354,509, entitled, “Wastewater Treatment System,” discloses a wastewater treatment system comprising means of decontaminating wastewater; means of measuring control parameters of the wastewater; means for controlling said decontamination; and a programmable logic controller. The user is able to receive control parameter data and control the various processes of the wastewater treatment system from a remote location.
U.S. Pat. No. 7,300,591, entitled, “Wastewater Treating Method and Wastewater Treating Apparatus,” discloses a wastewater treating technique for treating nitrogen compounds in a for-treatment wastewater by an electrochemical technique, wherein at least portions of a pair of electrodes is immersed in the for-treatment wastewater; a material of one electrode constituting an anode is an insoluble conductor; and a material of the other electrode constituting a cathode is an element in the group VIII of the periodic table, a conductor containing the element in the group VIII, or a conductor covered with the element in the same group or the conductor containing the element in the same group.
U.S. Pat. No. 6,960,301, entitled, “Leachate and Wastewater Remediation System,” discloses a compact portable modular wastewater treatment system which integrates several processing technologies to provide a substantially purified water source. A wastewater stream is sent through an initial filtration step. The filtered wastewater is then subjected to electrocoagulation and then further filtered. The resulting stream containing substantially only organics is then treated in an advanced oxidation process which can include passing an electrical current through the water during the oxidation process. The partially treated water is then passed through ion-exchange columns to polish ammonium and other contaminants. The ion-exchange columns are cycled through regeneration cycles to provide a continuous ion-exchange medium. The ammonium rich brine solution used in regeneration is subjected to an ammonium destruct process and then reused in regenerating ion-exchange columns. The water can then be sent through a final disinfection oxidation process to destroy or inactivate pathogens and/or remove any remaining colorants or odor to provide a water source suitable for almost any use.